1. Field of the Invention
The invention relates to a magnetic head which performs recording or reproduction on a magnetic recording medium, and particularly to a narrow-track magnetic head for high density recording which is useful in a digital VTR or the like, a method of producing the same, and a magnetic recording/reproduction apparatus.
2. Description of the Prior Art
In a system such as a digital VTR wherein a large amount of signals are recorded and reproduced, it is essential to employ high density magnetic recording/reproduction techniques such as the narrow-track technique and the short-wavelength technique.
Generally, it is known that high density magnetic recording/reproduction can be attained when the coercive force of a magnetic medium is increased and the saturation magnetic flux density (hereinafter, referred to as "Bs") of a magnetic head is increased. A ferrite material which has mainly been used in the prior art as a magnetic head material has Bs of about 0.5 T. When a ferrite magnetic head is used for a metal tape having a coercive force as high as 80 kA/m or more, therefore, there occurs magnetic saturation so that recording cannot be conducted satisfactorily. To comply with this, research efforts have vigorously been conducted on magnetic heads using a material which has a Bs larger than ferrite, such as a Sendust alloy material (Bs: about 1.0 T), a Co amorphous film (Bs: about 0.8 to 1.1 T), or a novel material such as a Co superstructure nitriding alloy film having a Bs of 1.3 T or more, an Fe superstructure nitride film, or an Fe nitride film, particularly on a composite magnetic head or so-called MIG head in which the main core is made of ferrite and a magnetic thin film is disposed at least in the vicinity of the front gap.
FIG. 10 shows the configuration of a MIG head. A pair of convex magnetic cores 2 and 3 which are opposed to each other through a magnetic gap 1 respectively comprise convex core bodies 4 and 5 made of ferrite, and high saturation magnetic flux density films 6 and 7 which cover the respective projection end faces of the core bodies and both the side faces elongating therefrom. The two magnetic cores 2 and 3 are coupled to each other by a pair of glass blocks 8 and 9 which are disposed at their both sides. The reference numeral 10 designates a winding hole through which coils can pass.
In such a magnetic head, as shown in FIG. 11 in detail, track dis-adjustments d.sub.1, and d.sub.2 are easily produced by production errors due to machining accuracy of track grooves 4a and 5a of the pair of core bodies 4 and 5, and butting accuracy of the core bodies 4 and 5. Moreover, the presence of rounds 2a, 2b, 3a and 3b of edge portions of the magnetic films 6 and 7 further impairs the track width accuracy.
In high density recording, these divergences and rounds of the edges tend to cause impairment.
As partly disclosed by U.S. Pat. No. 4,110,902, a method of regulating the track width by using a wire on a sliding face may be employed. In the method, however, the whole of the sliding face is machined so as to have a fixed track width, and the running of a magnetic medium causes a problem of abrasion resistance. Furthermore, magnetic properties are greatly impaired. According to the invention, a machining process is conducted only on the vicinity of a gap, and therefore the problem of abrasion resistance and the impairment of magnetic properties do not occur.
U.S. Pat. No. 3,668,775 discloses a configuration in which the whole of a core constitutes the track width. Also in this configuration, magnetic properties are greatly impaired. Moreover, the chip has a reduced strength.
U.S. Pat. No. 5,208,965 discloses a method in which a track width is regulated by track width regulation grooves. In the disclosed method, cores are separately machined, and then butted to be joined to each other, thereby producing butting errors. Therefore, the method cannot be employed in a production of a narrow-track width head.
Recently, the track width and its accuracy are requested to be 10 .mu.m or less and .+-.0.5 .mu.m, respectively. As described above, however, it is substantially impossible according to the prior art to produce a magnetic head which fulfills the requirements while preventing the magnetic properties from being impaired.